Implantable medical devices (IMD), such as pacemakers or other cardiac devices, may be used to deliver electrical stimulation therapy to a patient's heart to treat a variety of symptoms or conditions, such as heart failure and arrhythmia. In general, an IMD delivers cardiac stimulation therapy in a form of electrical pulses. An IMD may deliver cardiac stimulation therapy via one or more leads that include one or more electrodes located within in or proximate to the heart.
In general, a physician selects values for a number of programmable parameters in order to define the electrical cardiac stimulation therapy to be delivered by the IMD to a patient. For example, the physician ordinarily selects a combination of electrodes carried by one or more implantable leads, and assigns polarities to the selected electrodes. In addition, the physician may select an amplitude, which may be a current or voltage amplitude, and a pulse width for stimulation pulses to be delivered to the patient. The physician may also select chambers of the heart to which therapeutic stimulation should be delivered, select a mode of cardiac pacing, select a progression of anti-tachyarrhythmia therapies, and select values for a number of other programmable parameters, such as escape, atrioventricular, or inter-ventricular intervals.